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Chockstone Forum - General Discussion

General Climbing Discussion

 Page 1 of 2. Messages 1 to 20 | 21 to 21
Author
Vector Forces
handtraverse
3/06/2006
11:53:51 PM
I read Phil Box's article on tyrolean traverse and found it to be interesting. So, I began to do extra research on the vector forces invovled when you consider the angle in the rope created by the weight of the one hanging on it. (I'm not a mathemetician - just a small business owner - wood restorations and faux effects).

To make my question simple, as we all know with anchors, the greater the angle, the greater the force is on the anchor webbing, cords, whatever. By contrast, in a tyrolean traverse set up, the rope is straight, obviously. Now here's my question:

Then when one hangs from it...does the vector force which is initiated create huge weight forces, similar to a multi-point anchor where the slings, let's say, are at a 150 degree angle, which creates huge forces. Oh, and not to forget that the rope for tyrolean traverse has already been tensioned! Whew!

Thank you for any help. I think the forces on the equipment is scarier than the ride would be!
handtraverse
5/06/2006
12:00:16 AM
ti, thanks for your time in giving an answer to my question. Albeit I'm not a mathemetician so I don't understand your formulation(not that I doubt your accuracy). However, I do have a general understanding of vectors and their potential forces from reading in dictionaries and physics sites.
I think that you did answer my question in general that there are indeed extreme forces applied in a tyrolean traverse set up. And that special care needs to be taken as this is especially dangerous. I did set up a tyrolean traverse in my back yard prior to this post.
When I was tensioning the line is when I realized I must be really stressing the rope, nevermind the anchors! FYI I used a 10.5mm dynamic rope.

Finally, let me ask this: I weigh 200 lbs. Is it safe for me to span 100 feet of 10.5mm dynamic rope for tyrolean traverse?

Thanks again - Tom
uwhp510
5/06/2006
11:12:46 AM
The key point from the diagram is that your weight (200 lbs) is supported by the vertical components of the tension in the line. The distance you are spanning is irrelevent. The angle is the important bit. The total tension in the line is found by your weight divided by the sine of the angle that the line makes with the horizontal when it is loaded up.
handtraverse
5/06/2006
12:07:49 PM
Hi Ti, What happens to the anchor? By your illustration it looks like a typical bomber to bomber run with at least one end or both ends using 1" webbing with a biner(you'll have to leave behind of course). If either or both of the anchors are 2 point anchors, as long as the angle is somewhere around 45 degrees or less, combined with the dynamic stretch of the rope, the anchors themselves I believe will be within their "normal" load ranges. The only other consideration, however minor, is the downward pull on the anchor gear but that really isn't going to matter, needless to say...just an observation.

I greatly appreciate your replies to my questions. Here in New Jersey USA I'm 14 hours behind you guys in Australia. At the time of this writing it's10.01pm Sunday, At the same time it's 12.01pm Monday for you. If I seem a bit slow to respond to anyone sometimes, that may very well be the reason! And come to think of it you might be answering my question before I ask it! Hee hee.

Anyway, I find the technical knowledge associated with climbing fun as well as climbing is fun...espesially when I run into precarious situations on the rock, I can feel more confident when I know the capabilities of all my gear.

Cheers! Tom
One Day Hero
6/06/2006
6:50:28 PM
I know tight tyrolians look really bad on paper, but check out a 'slackliner' sometime. The first time I saw someone wind a slackline up really tight I was sure biners were going to snap. Despite some really shallow angles <20 degrees, and large people bouncing on them, I've never seen a slackrope snap, so I would now have a lot of faith in a tyrolean, as long as the anchors were good.
paul
7/06/2006
10:05:02 AM
To make tyroleans less scary with the forces applied just double the ropes and anchors up, i've found that the petzl tamdam pulley is great for this as it allows you to attach a second pulley above it.
mockmockmock
7/06/2006
7:17:03 PM
I was under the impression the issue with those loading angles will be shock loading not ( I don't know what to call it ) loading of the traverse.

Having said that Dan Osmands later sport would have to be the greatest test of those loading angles. I think you'll be right over 100 feet.

Ralph.

BTW I can't back that up
handtraverse
8/06/2006
10:20:27 AM
Hi mockmockmock, let me say this first - Sorry if I misunderstood what you were commenting about and now I'm telling you something you already know! But here goes anyway!

The angles, actually the...angle in the rope associated with a tyrolean traverse, which is created by the weight of your body, pulls down on the rope, creating a new set of physics which falls within the definition of vector forces. This force amplifies the stress considerably, in a way similar to anchor slings which are set at extremely wide angles. Without the weight, the rope would be in a straight line. And in addition to everything else, the rope is tightened up somewhat before weighting it.

I'm still learning so don't believe evrything I say!!!!


Tom


paul
8/06/2006
11:53:47 AM
On 7/06/2006 mockmockmock wrote:
>I was under the impression the issue with those loading angles will be
>shock loading not ( I don't know what to call it ) loading of the traverse.

The angles will increase the forces on the anckore regardless of weather it is a static load or shock loading. Going on the calculations above if you have your rope tensioned with an angle of 179 degrees that is about 600% of your load on each anchor. factor in the strength lost in the rope where knotts are (20-25% for a figure eight) and the 10% safe working load which we like to use, then things would start to get scary even with a static load.

>Having said that Dan Osmands later sport would have to be the greatest
>test of those loading angles. I think you'll be right over 100 feet.
>
>Ralph.
>
>BTW I can't back that up

I believe that Dan Osman's setups used energy absorbers to help reduce the forces applied.
mockmockmock
8/06/2006
6:49:29 PM
I did say I could not back that up.

I'll take that under advisement but what I was getting at was given the choice of a steady load on 179* anchors or a dynamic load the chance of ripping one might be dramaticaly less on the steady load. I was unaware of the absorbers used by DO.

You may return to normal transmissions.

Ralph

The good Dr
8/06/2006
7:36:54 PM
Whether you have a static load or dynamic load, if the load is identical the same force is applied to the anchors. What changes is the load cycle. This impacts on the materials in the system in different ways (eg a constant force versus a 'momentary' force).

If the system will fail at say 12kN, whether this force is generated statically or dynamically does not matter, failure will still occur.

As a matter of practise, it is difficult to achieve angles in a rope based system that are greater than 160 degrees, and for a tyrolean you do not need to do so. The line may look virtually horizontal without the load on it, but will 'V' under load. A suitable pulley on the line makes it relatively easy to move across.

IdratherbeclimbingM9
9/06/2006
9:21:09 AM
ODH wrote
>I know tight tyrolians look really bad on paper, but check out a 'slackliner' sometime. The first time I saw someone wind a slackline up really tight I was sure biners were going to snap. Despite some really shallow angles <20 degrees, and large people bouncing on them, I've never seen a slackrope snap, so I would now have a lot of faith in a tyrolean, as long as the anchors were good.

& P wrote
>if you have your rope tensioned with an angle of 179 degrees that is about 600% of your load on each anchor.

Gonna be grief for the top anchor on the Tote some day !

Wouldn't want to be on that tyrolean then, especially if the top block of the Totem Pole actually shears off ...
It would make Paul Pritchard’s accident there, seem lightweight.
handtraverse
9/06/2006
11:09:08 AM
Paul wrote:
>The angles will increase the forces on the anckore regardless of weather
>it is a static load or shock loading. Going on the calculations above if
>you have your rope tensioned with an angle of 179 degrees that is about
>600% of your load on each anchor. factor in the strength lost in the rope
>where knotts are (20-25% for a figure eight) and the 10% safe working load
>which we like to use, then things would start to get scary even with a
>static load.

Ahh, yes, knots, I forgot about those important little things.

However, I'm not sure that the anchors in a tyrolean traverse would be feeling the same pain as the rope is. Maybe someone can clarify this point...it is a good point. If the anchors are set at, say, 20% angle or less, the force applied under normal conditions would distribute the weight 50/50 on each arm of the anchor. As the angle increases...well, you may have seen this diagram on Rock2 University of Oregon Website.

Tom
timc
9/06/2006
11:18:53 AM
From a novice. and I'm not sure if it's a silly question?
I understand the discussion is on vectors for horizontal lines. I was recently reading John Long's book
on 'Climbing Anchors' and on page 64 he has a SLCD and tri-cam rigged vertically with both pieces
equally loaded with a climber attachment pulling from the centre.



My question is, If you turn this setup horizontally I wouldn't use it. So assuming there is equal loading on
both peices of protection how do the vector forces apply vertically?

IdratherbeclimbingM9
9/06/2006
11:46:37 AM
>My question is, If you turn this setup horizontally I wouldn't use it. So assuming there is equal loading on both peices of protection how do the vector forces apply vertically?

I too am a novice regarding theory of forces involved, but would differentiate a tensioned tyrolean or slackline, from protection pieces placed in opposition to each other in a belay setup.

In the 1st considerable forces have already been applied. In the 2nd it is assumed that the predominant load will come onto either the upward holding piece OR the downward loaded piece, but not necessarily equally to both as an outward loading?
If the outward load is likely (ie predominant) then both pieces would have to hold the equivalent force of that loading (independently as it would be equally given full loading to both pieces), and if one failed then the whole shebang could/would fail.

Don't know anything about vector forces but placing pieces in opposition is an old climbing trick from way back and works well in horizontal breaks as well as vertical cracks. The setup is often rigged such that one piece takes the majority of the load however, and the secondary piece simply redirects the force or ensures the piece intended to hold the load is not dislodged by rope-drag etc.
timc
9/06/2006
12:03:26 PM
Understood cheers! Although the question about vector forces applying remains outstanding
If the load was not set to be predominantly on either piece of protection and the force was in an outward
direction (in the circumstance of a 'hanging belay'). Do vector angle and specifications apply for vertical
setups? (sorry to ask again)

IdratherbeclimbingM9
9/06/2006
12:11:10 PM
From practical experience (hanging belays and also hauling loads from same), the force predominantly comes onto the piece set for taking downward loading. It is possible to considerably load the opposition piece and theoretically this load can be equal to that which the non-opposition (ie 'main') piece is holding.

In my experience the pieces will often move a little and stems on cams etc tend to re-align themselves in the direction of loading.
With 3:1 pulley systems I have managed to bend bolt brackets in some situations though ...
... which is scary when I think about it in hindsight.

~~~~~~~~~~~~~~~~~~~~~~~~~
Post edit.
Another scary thought is that I have just passed the 2000 post mark (with this one) and joined the illustrious ranks of my predecessors nmonteith and Hex.
... Dalai follows closely .... theme music from jaws playing in background ...
uwhp510
9/06/2006
2:59:24 PM
It's all about the components of forces (there is no such thing as a scalar force, all forces have a magnitude and a direction, making them vectors, in which case they have components in different directions).

The weight of the person on the tyrolean is balanced by the vertical components of the tension in each side of the rope, each of which is balanced by the force applied to the rope by the anchor at that end. Regardless of where you are on the tyrolean, the tension in the rope is equal on either side of you (if it wasn't it would just slide through the pulley), hence the forces on the anchors are equal. And since there are two "anchor" forces whose vertical components are balancing your weight, each only feels half of your equivalent load. The surprising thing is that since the tension is equal to the load on the anchors, the rope only feels half of your equivalent load as well (maybe its not that surprising since you do have two bits of rope supporting you; think of the limiting case where the anchors are both in the same spot, so the angle is zero).

So in answer to Tom's question, the anchors are feeling the same "pain" as the rope.

Phil Box
9/06/2006
3:58:41 PM
On 9/06/2006 M9iswhereitsat wrote:
>Another scarey thought is that I have just passed the 2000 post mark (with
>this one) and joined the illustrious ranks of my predecessors nmonteith
>and Hex.
>... Dalai follows closely .... theme music from jaws playing in background
>...

This taken from rc.com.

Your losertude is confirmed. ;))
handtraverse
10/06/2006
8:49:26 AM
uwhp510 wrote:
>It's all about the components of forces (there is no such thing as a scalar
>force, all forces have a magnitude and a direction, making them vectors,
>in which case they have components in different directions).
>
>The weight of the person on the tyrolean is balanced by the vertical components
>of the tension in each side of the rope, each of which is balanced by the
>force applied to the rope by the anchor at that end. Regardless of where
>you are on the tyrolean, the tension in the rope is equal on either side
>of you (if it wasn't it would just slide through the pulley), hence the
>forces on the anchors are equal. And since there are two "anchor" forces
>whose vertical components are balancing your weight, each only feels half
>of your equivalent load. The surprising thing is that since the tension
>is equal to the load on the anchors, the rope only feels half of your equivalent
>load as well (maybe its not that surprising since you do have two bits
>of rope supporting you; think of the limiting case where the anchors are
>both in the same spot, so the angle is zero).
>
>So in answer to Tom's question, the anchors are feeling the same "pain"
>as the rope.

Wow! I stand corrected. Thanks much. At least at one point earlier in this conversation I did say... !!!!!!!!

Tom

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